Increasing compressor peak flow via higher-pressure gas injection

ABSTRACT

Embodiments of a system for increasing the flow rate of a compressor system are provided. The system includes a gas inlet component, a compression component including a compressor; and an injection component having a compression component connection connected to one or more chambers of the compressor. By injecting a secondary high-pressure gas stream into the compressor through the injection component, the discharge flow rate of the compressor system may be increased above the flow rate capable based on the design of the compressor, without additional equipment or unduly increasing power consumption of the compressor system.

TECHNICAL FIELD

The disclosed technology relates generally to compressors for compressed natural gas (CNG), and more particularly to methods and systems for increasing the flow rate of positive displacement compressors.

DESCRIPTION OF THE RELATED ART

The use of compressed natural gas (CNG) as a fuel source continues to grow around the world. CNG combustion produces less harmful and undesirable byproducts than gasoline or other petroleum-based products, and is safer than other fuels in the event of a spill because it disperses quickly in air.

Most conventional CNG stations are custom designed for specific site conditions, and must operate within predetermined inlet gas pressure and flow ranges. Such stations usually take a long time to build, and they are difficult to relocate from one location to another since they are designed to meet specific site conditions. According to other known CNG designs, the site conditions are modified to meet the equipment design specifications by utilizing an inlet gas regulator. Due to compressor design limitations, these stations often have to sacrifice gas pressure by going through the inlet regulator. After the gas is de-pressurized by the inlet regulator, it is then re-pressurized in the compressor. This design is very energy inefficient since the gas pressure is lowered before recompression in the compressor. Both custom-designed and site-modified systems are generally fixed speed and do not permit flow capacity control.

Most CNG stations utilize positive displacement compressors. Positive displacement compressors reduce gas volume to increase gas pressure. Such compressors draw in and capture a volume of gas in a chamber or cylinder, and then compress the gas within the chamber. Examples of positive displacement compressors include reciprocating piston compressors, rotary screw compressors, rotary vane compressors, and scroll compressors.

Several factors affect the discharge flow rate of positive displacement compressors. In single- and multi-stage positive displacement compressors, the size of the first (or only) compression chamber limits the initial volume of gas that may enter the compressor at one time. Further, the swept volume and stroke length impact the amount of compression achievable within each compression chamber. The combination of these variables determine the discharge flow rate of the compressor

BRIEF SUMMARY OF EMBODIMENTS

According to various embodiments of the disclosed technology, the peak discharge flow rate of a positive displacement compressor is increased by injecting a secondary high-pressure gas stream into one or more of the compression chambers. The secondary high-pressure gas stream increases the total amount of gas goes into the compression chamber, compensating for volumetric inefficiency arising from the sizes of preceding chambers or discrepancies in the incoming gas stream from the local gas utility or preceding compression chambers. The secondary high-pressure gas and the inlet gas are compressed together, achieving an increased discharge flow rate.

In accordance with the technology of the present disclosure, a system is provided to increase the discharge flow rate of a compressor. A natural gas stream from a gas inlet component is directed into a compression component including a single- or multi-stage compressor. An injection component is connected to the compressor of the compression section, which injects a secondary high-pressure gas into the compressor, thereby increasing the discharge flow rate of the compressor.

Other features and aspects of the disclosed technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the disclosed technology. The summary is not intended to limit the scope of the technology described herein, which are defined solely by the claims attached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The technology disclosed herein, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the disclosed technology. These drawings are provided to facilitate the reader's understanding of the disclosed technology and shall not be considered limiting of the breadth, scope, or applicability thereof. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.

FIG. 1 is a diagram of an example embodiment of a discharge flow rate increasing system in accordance with the present disclosure.

FIG. 2 is a diagram of another example embodiment of a discharge flow rate increasing system in accordance with the present disclosure.

The figures are not intended to be exhaustive or to limit the technology to the precise form disclosed. It should be understood that the technology can be practiced with modification and alteration, and that the disclosed technology be limited only by the claims and the equivalents thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the technology disclosed herein are directed towards a system of increasing the discharge flow rate of positive displacement compressors. In particular, the present disclosure utilizes the injection of a secondary high-pressure gas stream into one or more compression chambers to increase the discharge flow rate of the compressor. The injection of a secondary high-pressure gas into one or more compression chambers of a compressor compensates for volumetric inefficiencies due to the compressor design, resulting in a greater discharge flow rate than the compressor design would output. For CNG stations, this allows the station to increase the discharge flow rate of the compressor without unduly increasing the power consumption of the compressor, or needing additional equipment to increase the discharge flow rate of the CNG station.

Conventional CNG stations receive a natural gas supply from a local gas utility company. The local gas utility company operates the infrastructure necessary for transporting natural gas to different customers, and accordingly needs to track the amount of gas being used by customers. To do this, the utility company will build a meter set assembly (MSA) on site to measure the amount of gas transferred to the station. In addition, the natural gas is generally transported at low pressure through the utility company's infrastructure, in some cases as low as 20 psig. For CNG station use, the natural gas needs to be compressed to a higher operating pressure. In some cases, the natural gas needs to be compressed to a pressure of 3600 psig to 4500 psig. CNG stations utilize compressor systems to take the lower-pressure natural gas from the utility company and increase the gas to operating pressure.

FIG. 1 illustrates an example compressor system 100 in accordance with the present disclosure. The compressor system 100 includes a gas inlet component 110, a compression component 120, a gas injection component 130, a valve control and storage component 140, and a dispensing component 150. In various embodiments, the gas inlet component 110 may be provided at the site location by a local gas utility company. In various embodiments, the gas inlet component 110 may be the MSA installed by the local gas utility company. In some embodiments, the gas inlet component 110 may be some other natural gas source, such as a CNG tube trailer.

The compressor system 100 includes a compression component 120, including a compressor 122. The compressor 122 is a positive displacement compressor. Non-limiting examples of positive displacement compressors include: reciprocating piston compressors; rotary screw compressors; rotary vane compressors; and scroll compressors. In some embodiments, more than one compressor 122 may be included within compression component 120. In various embodiments, compressor 122 may be a single-stage or a multi-stage compressor. A single-stage compressor uses only one stage of compression to increase the pressure of natural gas. In a multi-stage compressor, multiple compression chambers are connected in series, with the pressure of the gas increasing as it passes through each stage.

The compression component 120 is in fluidic communication with the gas inlet component 110, such that a natural gas stream introduced into the compressor system 100 via the gas inlet component 110 is introduced into the compression component 120. In various embodiments, the fluidic communication may be through directly connecting the compression component 120 and the gas inlet component 110, as illustrated in FIG. 1. In some embodiments, additional processing components may be connected between the gas inlet component 110 and the compression component 120. The additional components may process the incoming natural gas stream prior to introducing the stream into the compression component 120. FIG. 2 illustrates a dryer component 210 disposed between the gas inlet component 110 and the compression component 120. FIG. 2 is discussed more below.

Referring back to FIG. 1, the compressor system also includes a gas flow control component 140. The gas flow control component 140 includes one or more storage vessels 142 and a valve control panel 144. The storage vessels 142 are designed to store CNG outputted from the compression component 120 to ensure a supply of high-pressure CNG for station purposes, such as refueling CNG-powered vehicles. In various embodiments, the valve control panel 144 may direct CNG outputted from the compression component 120 into the storage vessels 142. In some embodiments, the valve control panel 144 may direct the CNG outputted from the compression component 120 to a dispensing component 150. In various embodiments, dispensing component 150 may be a refueling pump at a CNG station.

To increase the discharge flow rate of the compressor 122 in the compression component 120, an injection component 130 is included. In various embodiments, the injection component 130 may include a control valve. Non-limiting examples of control valves include: orifice plate; regulator; needle valve; proportional valve; diaphragm valve. In such embodiments, a PID controller may be included to control the operation of the control valves. In some embodiments, the injection component 130 may include multiple control valves, as illustrated in FIG. 1. In some embodiments, manual valves may be included in the injection component 130. In various embodiments, a combination of control valves and manual valves may be included in the injection component 130.

The injection component 130 is designed to inject a secondary high-pressure gas stream (a gas at a higher-pressure than the natural gas stream) into the compressor 122. In various embodiments, the source of the secondary high-pressure gas may be the storage vessels 142. The valve control panel 144 may direct a gas stream from the storage vessels 142 into the injection component 130.

In various embodiments, the source of the higher-pressure gas may be the output from adjacent compression component or compression component 120 itself. As discussed above, the CNG outputted from the compression component 120 may be directed to different components by the valve control panel 144. In some embodiments, the valve control panel 144 may direct the CNG outputted from the compression component 120 directly to the injection component 130. In this way, the CNG resulting from the compression process is circulated back into the compressor 122. The outputted CNG is at a higher pressure than the natural gas stream within the compressor, thereby achieving the same potential increase in discharge flow rate as possible by using a different, unaffiliated source of higher-pressure gas.

The injection component 130 includes a compression component connection 132. The compression component connection 132 connects to the compressor 122 in the compression component 120, injecting the higher-pressure gas stream from the injection component 130 into the compressor 122. In various embodiments, a valve may be included on the compression component section 132.

In various embodiments, the compressor 122 may be a single-stage compressor having a single compression chamber, and the compression component connection 132 may be connected to the compression chamber.

In various embodiments, the compressor 122 may be a multi-stage compressor having multiple compression chambers, and the compression component connection 132 may be connected to one of the multiple compression chambers. In some embodiments, the compression component connection 132 could be connected to the first compression chamber. In other embodiments, the compression component connection 132 may be connected to the final compression chamber of the compressor 122, as illustrated in FIG. 1. For example, where the multi-stage compressor has four (4) compression stages, the compression component connection 132 may be connected to the fourth compression stage. In other embodiments, the compression component connection 132 may be connected to an intermediate compression chamber of the compressor 122.

In a single-stage compressor, the increase in discharge flow rate is dependent on the amount of higher-pressure gas injected into the compressor. In a multi-stage compressor, which chamber the higher-pressure gas is injected into also impacts the overall increase in the discharge flow rate. For example, if the compression component connection of the injection component is connected to the first compression chamber of a multi-stage compressor, the flow rate from the first chamber would be equivalent to the same amount of higher-pressure gas injected into a single-stage compressor. The flow rate leaving the subsequent chambers, however, is still limited by the gas stream leaving the first chamber. At the same time, connecting the compression component connection of the injection component to the last compression chamber would alleviate the impact of limitations from the design of the preceding chambers. The location of the compression component connection of the injection component and the amount of higher-pressure gas injected into the compressor 122 may be dictated based on the intended design.

Further, the amount of higher-pressure gas that may be injected into any compression chamber is limited by the operating limits of the compression chamber utilized in the compressor 122. Such operating limits include rod load, temperature, cylinder pressure rating, among others.

In various embodiments, greater increase in discharge flow rate may be possible by injecting higher-pressure gas into multiple chambers of a multi-stage compressor. FIG. 2 illustrates a compressor system 200 with multiple points of higher-pressure gas injection into the compressor 122 in accordance with the present disclosure. In various embodiments, the compressor system 200 may include the same components as in the compressor system 100 of FIG. 1. As shown in FIG. 2, an additional dryer component 210 is positioned between the gas inlet component 110 and the compression component 120. As discussed above, additional processing components—such as dryer component 210—may be included in a compressor system in accordance with the present disclosure. The natural gas stream passes through the dryer component 210 to remove excess liquid from the natural gas, which may cause issues for other components down the line, such as control valves. Although a dryer component 210 is included, the gas inlet component 110 and the compression component 120 remain in fluidic communication as the natural gas stream from the gas inlet component 110 flows through the additional components and enters the compression component 120 before being used at the CNG station.

As illustrated in FIG. 2, the injection component 130 has three (3) compression component connections 132. In various embodiments, greater than three compression component connections 132 may be included in the injection component 130. In various embodiments, valves may be included on each compression component connection 132. In such embodiments, the station may select the one or more compression component connections 132 may be opened to inject higher-pressure gas into the compressor 122 based on the needs of the station at any given time. This adjustability allows for compression component connections 132 to be included in the injection component 130 such that any potential arrangement may be used, without having to redesign the station or install additional components.

Each compression component connection 132 is connected to one chamber of the compressor 122. In various embodiments, the injection component 130 may include the same number of compression component connections 132 as the number of compression stages in the compressor 122. In other embodiments, the compression component 120 may include multiple single-stage compressors 122, and the injection component 130 may include the same number of compression component connections 132 as the number of single-stage compressors 122, such that each compression component connection 132 is paired with a single-stage compressor 122. In some embodiments, the injection component 130 may include less than the same number of compression component connections 132 as the number of compression stages of a multi-stage compressor, or the number of single-stage compressors, included in compression component 120. In such embodiments, the compression component connections 132 may be connected depending on the resulting increase in discharge flow rate.

Compressor systems in accordance with the present disclosure show an increase in the discharge flow rate without the need for additional equipment or unduly increasing the power consumption of the compressor system as designed. For example, measurements were taken of a compressor system including a four-stage compressor. Baseline measurements were taken with the compressor system configured as designed, without any higher-pressure gas injection. Measurements were than taken with the compressor system configured in accordance with the present disclosure, where the higher-pressure gas was injected into the fourth (final) stage of the compressor. The injection component included a manual valve, which was adjusted to gradual increase the amount of higher-pressure gas injected into the fourth stage.

The measurements for each configuration were taken with a natural gas stream from the inlet having a pressure of 30 psig. The following table illustrates the results of the testing. The discharge flow rate was measured in standard cubic feet per minute (scfm) and the power consumption was measured in amps (A):

Compressor Compressor System System as in Accordance with Designed Present Disclosure Flow Capacity (@ 640 scfm 1500-1950 scfm (adjustable by 30 psig site inlet) manual valve) Power Draw (400 bhp 386 A 410 A motor-460 V, 60 Hz, 3 phase)

As illustrated by the results, the injection of higher-pressure gas into the final stage resulted in an increase of 860-1310 scfm in the flow rate of the compressor system over the flow rate as designed. The maximum recorded flow capacity of 1950 scfm was limited by the size of the manual valve, higher flow capacity might be achievable with a larger manual valve. The compressor system with injection into the fourth chamber also showed no major issues over 80 hours of operation. By pairing a suitable injection component with the maximum operational parameters of the compressor, embodiments in accordance with the present disclosure can achieve over a three-fold increase in the flow rate of a compressor system over the flow rate as designed.

While various embodiments of the disclosed technology have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the disclosed technology, which is done to aid in understanding the features and functionality that can be included in the disclosed technology. The disclosed technology is not restricted to the illustrated example architectures or configurations, but the desired features can be implemented using a variety of alternative architectures and configurations. Also, a multitude of different constituent module names other than those depicted herein can be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise.

Although the disclosed technology is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed technology, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the technology disclosed herein should not be limited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration. 

What is claimed is:
 1. A system, comprising: a gas inlet component; a compression component comprising a compressor; and an injection component having a compression component connection connected to the compressor; wherein the injection component injects a secondary high pressure gas stream into the compressor.
 2. The system of claim 1, wherein the high pressure gas stream is directed from one or more storage vessels to the injection component by a valve control panel.
 3. The system of claim 1, wherein the high pressure gas stream is directed from an output of the compression section to the injection component by a valve control panel.
 4. The system of claim 1, wherein the compressor comprises a plurality of compression stages.
 5. The system of claim 4, wherein a first compression stage is in fluidic communication with the gas inlet component, and the injection component is connected to the first compression stage.
 6. The system of claim 4, wherein the injection component is connected to the last compression stage of the plurality of compression stages.
 7. The system of claim 4, the injection component comprising a plurality of compressor component connections, wherein each compression component connection is connected to one of the plurality of compression stages.
 8. The system of claim 1, wherein the compressor comprises a plurality of compression stages.
 9. The system of claim 8, wherein a first compression stage is in fluidic communication with the gas inlet component, and the injection component is connected to the first compression stage.
 10. The system of claim 8, wherein the injection component is connected to the last compression stage of the plurality of compression stages.
 11. The system of claim 8, the injection component comprising a plurality of compression component connections, wherein each compression component connections is connected to one of the plurality of compression stages.
 12. The system of claim 1, the compression component comprising a plurality of compressors.
 13. The system of claim 12, wherein the injection component is connected to exactly one of the plurality compressors.
 14. The system of claim 12, the injection component comprising more than one compression component connections, each compression component connection connected to one of the plurality compressors.
 15. A system, comprising: a CNG station for refueling motor vehicles, the CNG station comprising: a gas inlet component; a compression component comprising a reciprocating compressor, the compression component being in fluidic communication with the gas inlet component; a gas flow control component comprising one or more storage vessels and a valve control panel; a dispensing component; and an injection component having a compression component connection connected to the reciprocating compressor; wherein the injection component injects a secondary high pressure gas stream into the reciprocating compressor chamber.
 16. The system of claim 15, wherein the high pressure gas stream is directed from the one or more storage vessels to the injection component by the valve control panel.
 17. The system of claim 15, wherein the high pressure gas stream is directed from an output of the compression section to the injection component by the valve control panel.
 18. The system of claim 15, the reciprocating compressor comprising multiple compression stages and the injection component being connected to a final compression stage of the multiple compression stages.
 19. A system, comprising: a gas inlet component; a compression component comprising a reciprocating compressor having four compression stages, the compression component being in fluidic communication with the gas inlet component; a gas flow control component comprising one or more storage vessels and a valve control panel; a dispensing component; and an injection component having a compression component connection connected to the fourth compression stage of the reciprocating compressor; wherein the injection component injects a high-pressure gas stream into the fourth stage of the reciprocating compressor
 20. The system of claim 19, the injection component further comprising a valve for controlling the amount of high-pressure gas injected into the fourth stage of the reciprocating compressor.
 21. The system of claim 20, wherein the flow rate of the system with the valve closed such that no high-pressure gas is injected into the fourth stage is 640 scfm.
 22. The system of claim 20, wherein the flow rate of the system with the valve in a first position is 1500 scfm, and the flow rate of the system with the valve in a second position is 1950 scfm.
 23. The system of claim 22, wherein the flow rate of the system is between 1500 scfm and 1950 scfm when the valve is in a position between the first position and the second position. 